Human Insulins

HUMAN INSULINS

In the 1980s, the human insulins (having the same amino acid sequence as human insulin) were produced by recombinant DNA technology in Escherichia coli—‘proinsulin recombinant bacterial’ (prb) and in yeast— ‘precursor yeast recombinant’ (pyr), or by ‘enzymatic modification of porcine insulin (emp).

1. HUMAN ACTRAPID: Human regular insulin; 40 U/ ml, 100 U/ml, ACTRAPID HM PENFIL 100 U/ml pen inj., WOSULINR 40 U/ml inj vial and 100 U/ml pen injector cartridge.

2. HUMAN MONOTRAD: Human lente insulin; 40 U/ ml, 100 U/ml.

3. HUMAN INSULATARD, HUMINSULINN: Human isophane insulin 40 U/ml. WOSULINN 40 U/ml inj. vial and 100 U/ml pen injector cartridge.

4. HUMAN ACTRAPHANE, HUMINSULIN 30/70, HUMAN MIXTARD: Human soluble insulin (30%) and isophane insulin (70%), 40 U/ml. WOSULIN 30/70: 40 U/ml vial and 100 U/ml cartridge.

5. ACTRAPHANE HM PENFIL: Human soluble insulin 30% + isophane insulin 70% 100 U/ml pen injector.

6. INSUMAN 50/50: Human soluble insulin 50% + isophane insulin 50% 40 U/ml inj; WOSULIN 50/50 40 U/ml vial, 100 U/ml cartridge.

In the USA and Europe the use of human insulins has rapidly overtaken that of purified animal insulins: in Britain now > 90% diabetics who use insulin are taking human insulins or insulin analogues. Human insulin is more water soluble as well as hydrophobic than porcine or bovine insulin. It has a slightly more rapid s.c. absorption, earlier and more defined peak and slightly shorter duration of action.

The allegation that human insulin produces more hypoglycaemic unawareness has not been substantiated. However, after prolonged treatment, irrespective of the type of insulin, many diabetics develop relative hypoglycaemic unawareness/change in symptoms, because of autonomic neuropathy, changes in perception/attitude and other factors. The cost of human insulin now is the same as that of pork MC insulin.

Superiority of human insulin over pork MC insulin has not been demonstrated. Though new patients may be started on human insulins, the only indication for transfer from purified pork to human insulin is allergy to pork insulin. It is unwise to transfer stabilized patients from one to another species insulin without good reason.

Though it is desirable to employ human/ highly purified pork insulin in all diabetics, in developing countries conventional insulin preparations are still used for economic reasons. Human/highly purified insulins are specially indicated in the following situations:

1)  Insulin resistance: especially when due to large amounts of insulin binding antibodies.

2)    Allergy to conventional preparations.

3)    Injection site lipodystrophy; changeover causes resolution of the lesions.

4)  Short-term use of insulin in diabetics who are otherwise stabilized on diet and exercise with/without oral hypoglycaemics, e.g. to tideover surgery, trauma, infections, ketoacidosis, etc.

5)    During pregnancy.

Insulin Analogues

Using recombinant DNA technology, analogues of insulin have been produced with modified pharmacokinetics on s.c. injection, but similar pharmacodynamic effects. Greater stability and consistency are the other advantages.

Insulin lispro: Produced by reversing proline and lysine at the carboxy terminus B 28 and B 29 positions, it forms very weak hexamers that dissociate rapidly after s.c. injection resulting in a quick and more defined peak as well as shorter duration of action. Unlike regular insulin, it needs to be injected immediately before or even after the meal, so that dose can be altered according to the quantity of food consumed. A better control of mealtime glycaemia and a lower incidence of late postprandial hypoglycaemia have been obtained. Using a regimen of 2–3 daily mealtime insulin lispro injections, a slightly greater reduction in HbA_1c compared to regular insulin has been reported. Fewer hypoglycaemic episodes occurred.

HUMALOG 100 U/ml inj.

Insulin aspart: The proline at B 28 of human insulin is replaced by aspartic acid. This change reduces the tendency for selfaggregation, and a timeaction profile similar to insulin lispro is obtained. It more closely mimics the physiological insulin release pattern after a meal, with the same advantages as above.

NOVOLOG, NOVORAPID 100 U/ml inj.

Insulin glulisine: Another rapidly acting insulin analogue with lysine replacing asparagine at B 23 and glutamic acid replacing lysine at B 29. Properties and advantages are similar to insulin lispro.

Insulin glargine: This longacting biosynthetic insulin has 2 additional arginine residues at the carboxy terminus of B chain and glycine replaces asparagine at A 21. It remains soluble at pH4 of the formulation, but precipitates at neutral pH encountered on s.c. injection. A depot is created from which monomeric insulin dissociates slowly to enter the circulation. Onset of action is delayed, but relatively low blood levels of insulin are maintained for upto 24 hours. A smooth ‘peakless’ effect is obtained. Thus, it is suitable for once daily injection to provide background insulin action. Fasting and interdigestive blood glucose levels are effectively lowered irrespective of time of the day when injected or the site of s.c. injection. Lower incidence of nighttime hypoglycaemic episodes compared to isophane insulin has been reported. However, it does not control mealtime glycaemia, for which a rapid acting insulin or an oral hypoglycaemic is used concurrently. Because of acidic pH, it cannot be mixed with any other insulin preparation; must be injected separately.

LANTUS OPTISET 100 U/ml in 5 ml vial and 3 ml prefilled pen injector.